﻿using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using System.ServiceProcess;

namespace CheeseDCOM
{
    public static class ServiceHelper
    {
        [DllImport("advapi32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
        public static extern Boolean ChangeServiceConfig(
            IntPtr hService,
            UInt32 nServiceType,
            UInt32 nStartType,
            UInt32 nErrorControl,
            String lpBinaryPathName,
            String lpLoadOrderGroup,
            IntPtr lpdwTagId,
            [In] char[] lpDependencies,
            String lpServiceStartName,
            String lpPassword,
            String lpDisplayName);

        [DllImport("advapi32.dll", SetLastError = true, CharSet = CharSet.Auto)]
        static extern IntPtr OpenService(
            IntPtr hSCManager, string lpServiceName, uint dwDesiredAccess);

        [DllImport("advapi32.dll", EntryPoint = "OpenSCManagerW", ExactSpelling = true, CharSet = CharSet.Unicode,
            SetLastError = true)]
        public static extern IntPtr OpenSCManager(
            string machineName, string databaseName, uint dwAccess);

        [DllImport("advapi32.dll", EntryPoint = "CloseServiceHandle")]
        public static extern int CloseServiceHandle(IntPtr hSCObject);

        private const uint SERVICE_NO_CHANGE = 0xFFFFFFFF;
        private const uint SERVICE_QUERY_CONFIG = 0x00000001;
        private const uint SERVICE_CHANGE_CONFIG = 0x00000002;
        private const uint SC_MANAGER_ALL_ACCESS = 0x000F003F;

        public static void ChangeStartMode(ServiceController svc, ServiceStartMode mode)
        {
            var scManagerHandle = OpenSCManager(null, null, SC_MANAGER_ALL_ACCESS);
            if (scManagerHandle == IntPtr.Zero)
            {
                throw new ExternalException("Open Service Manager Error");
            }

            var serviceHandle = OpenService(
                scManagerHandle,
                svc.ServiceName,
                SERVICE_QUERY_CONFIG | SERVICE_CHANGE_CONFIG);

            if (serviceHandle == IntPtr.Zero)
            {
                throw new ExternalException("Open Service Error");
            }

            var result = ChangeServiceConfig(
                serviceHandle,
                SERVICE_NO_CHANGE,
                (uint)mode,
                SERVICE_NO_CHANGE,
                null,
                null,
                IntPtr.Zero,
                null,
                null,
                null,
                null);

            if (result == false)
            {
                int nError = Marshal.GetLastWin32Error();
                var win32Exception = new Win32Exception(nError);
                throw new ExternalException("Could not change service start type: "
                                            + win32Exception.Message);
            }

            CloseServiceHandle(serviceHandle);
            CloseServiceHandle(scManagerHandle);
        }
    }
}